stringbufferdemo.java

本java源程序包括了大量的学习程序（共27章）方便大家学习

public class StringBufferDemo 
{
	StringBuffer strBuf1 = new StringBuffer("Hello world!");
	//声明、创建并初始化StringBuffer类的对象strBuf1
	StringBuffer strBuf2;
	//声明StringBuffer类的对象strBuf2
	StringBuffer strBuf3 = new StringBuffer(10);
	//声明并创建StringBuffer类的对象strBuf3，并设定其长度为10
	public StringBufferDemo()
	{
		strBuf2 = new StringBuffer("This is Java code.");
		//创建并初始化StringBuffer类的对象strBuf2
		strBuf3 = new StringBuffer("Hello");
		//创建并初始化StringBuffer类的对象strBuf3
		String output = "strBuf1:"+strBuf1.toString()+"\nlength="+
		                 strBuf1.length()+"\ncapacity="+strBuf1.capacity();
		//使用StringBuffer类的方法toString()，将StringBuffer类对象转化为String型字符串
		//使用StringBuffer类的方法length()，来获得该可变字符串的长度
		//使用StringBuffer类的方法capacity()，来获得该可变字符串的的最大存储容量
		System.out.println(output);
		strBuf1.setLength(30);
		//使用StringBuffer类的方法setLength()，来设置可变字符串的长度
		System.out.print("After add strBuf1's length,");
		System.out.println("strBuf1's capacity is:"+strBuf1.length());
		strBuf1.ensureCapacity(60);
		//使用StringBuffer类的方法ensureCapacity()，来设置可变字符串的最大存储容量
		System.out.print("Set strBuf1's capacity,");
		System.out.println("Now strBuf1's capacity is:"+strBuf1.capacity());		
		System.out.println();
		System.out.println("strBuf2:"+strBuf2.toString());
		System.out.println("Char at 0 in strBuf2 is:"+strBuf2.charAt(0));
		System.out.println("Char at 9 in strBuf2 is:"+strBuf2.charAt(9));
		char ch[] = new char[strBuf2.length()];
		strBuf2.getChars(8,12,ch,0);
		//使用StringBuffer类的方法getChars()，来获取strBuf2中第8~12位的字符
		System.out.println("The char from 8 to 12 is:");
		for(int i=0;i<4;i++)
		{
			System.out.print("\""+ch[i]+"\",");
		}
		System.out.println("\n");
		System.out.println("strBuf3:"+strBuf3.toString());
		System.out.print("After append string to strBuf3,");
		strBuf3.append(" world.StringBufferDemo!");
		//使用StringBuffer类的方法append()，在strBuf3末尾插入字符串
		System.out.println("New strBuf3:\n"+strBuf3.toString());
		System.out.print("After set the 5th char,");
		strBuf3.setCharAt(11,'!');
		//使用StringBuffer类的方法setCharAt()，来更改strBuf3中第11位的字符
		System.out.println("the new strBuf3:\n"+strBuf3.toString());
		
	}
	public static void main(String[] args) 
	{
		StringBufferDemo stringBufferDemo = new StringBufferDemo();
	}

}